1. Field of the Invention
This invention relates to endless, toothed belts, and, more particularly, to a toothed belt used to frictionally convey flat objects, such as paper money, cards, tickets, and the like.
2. Background Art
A prior art system for conveying thin articles, such as paper money, cards, tickets, etc. is shown at 10 in FIG. 1. The conveying system 10 includes cooperating, endless, toothed belts 12, 14, each having a similar construction. The belt 12 is trained around spaced drive and driven pulleys 16, 18, respectively, which pulleys 16, 18 have parallel rotational axes 20, 22. The belt 14 is trained around drive and driven pulleys 24, 26, which pulleys 24, 26 are rotatable about axes 28, 30, that are parallel to each other and the axes 20, 22 associated with the belt 12. The drive pulley 16 rotates in the direction of the arrow 32, with the drive pulley 24 rotating in the direction of the arrow 33.
The belts 12, 14 are arranged so that outside conveying surfaces 34, 36 on the belts 12, 14 are in contact over a substantial length thereof at the region 38. An article 40 to be conveyed, which article 40 may be paper money, cards, tickets, or the like, is advanced between the belts 12, 14 in the direction of the arrow 42. The article 40 is frictionally driven by the belt surfaces 34, 36 from right to left in FIG. 1 with the belts 12, 14 advancing as previously described. Spaced pressing rollers 44, 46 are selectively movable downwardly in FIG. 1 against the inside of the belt 12 at the region 38 to thereby deform and press the belt 12 towards backing rollers 48, 50, aligned with the pressing rollers 44, 46 and acting against the belt 14, to vary the pressing force between the belt surfaces 34, 36 at the region 38.
Ideally, the coefficient of friction between the article 40 and belt surfaces 34, 36 remains relatively constant through significant temperature variations, preferably in the range of -20.degree. C. to 60.degree. C. Still further, it is desirable that the flexibility and wear resistance of the belts 12, 14 do not significantly change with the belts 12, 14 operating within this temperature range. It is also important that the belts 12, 14 do not stain the articles 40 which are conveyed thereby.
It is known to construct toothed belts, such as those 12, 14, disclosed in FIG. 1, using chloroprene rubber. These belts have a plurality of regularly spaced teeth on an inside surface and an outside part within which load carrying cords are embedded.
It is also known to place a cloth covering over the surface of the teeth on this type of belt. One known cloth layer has a warp and a weft with the weft being defined by crimped 6 nylon or 6,6 nylon. The warp is an uncrimped thread of 6 nylon or 6,6 nylon, preferably with the same composition as the weft.
It is also known to enhance the adherence of the cloth to the belt teeth by using an adhesion treatment with a resorcin-formalin-latex solution (RFL). This solution is applied to the rubber using a soaking or a spreading treatment process.
Even when a chloroprene rubber which does not readily crystallize at low temperatures is used, when the chloroprene rubber is used alone, a decrease in the frictional coefficient between the belt and the articles to be conveyed may result at low temperatures. To compensate for this, the gripping force between the belts 12, 14 has been increased by deforming the belt through the pressing rollers 44, 46.
By urging the pressing rollers 44, 46 against the belt 12, the tension thereon increases. As a result, the surfaces 34, 36 become more prone to wear. Further, load carrying cords within the belt 12 tend to stretch. Adjustment of the belt tension through change in the spacing between the pulleys 16, 18 may then be necessary, possibly on a frequent basis. To accommodate this adjustment, the pulleys and supporting structure therefor have to be made strong and durable, which potentially increases the complexity and the cost of the overall system.
Another problem with conventional, toothed conveying belts is that the rubber underlying the cloth coveting layer is commonly exposed through openings defined between the warp and weft of the cloth layer. The pulleys 16, 18, 24, 26 may directly contact the rubber on the belts 12, 14 through these openings, and as a result abrade the rubber to produce rubber dust particles. This rubber dust may migrate between the belts 12, 14 in the region 38 and may contact and stain the articles 40 that are conveyed.